KLAU/BUENA VISTA MINEPASO ROBLES, CA

Cleanup Activities

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Background

Klau/Buena Vista Mine is located in San Luis Obispo County, California, about 12 miles west of Paso Robles. The site consists of two abandoned mercury mine sites (Klau and Buena Vista) located on adjacent properties on a northwest-southeast ridge of the Santa Lucia Range in the California coastal mountains. Mercury mining and ore processing operations took place at the mines between 1868 and 1970. Buena Vista Mines, Inc. has owned the Buena Vista Mine at least since 1957 and the Klau Mine since at least 1964. The most significant contaminant of concern is mercury, a metal that can be harmful to the human nervous system. Following initial actions to protect human health and the environment, site investigations and long-term cleanup planning are ongoing.

What Has Been Done to Clean Up the Site?

What Is the Current Site Status?

A remedial investigation to further assess the nature and extent of mercury in soil and water at the site finished in October 2012. The feasibility study finished in January 2014. As a result of data gaps, a two-year bioreactor treatability study is planned. A feasibility study addendum will be prepared documenting the results.

In the meantime, state and local authorities have numerous health advisories in place, warning anglers of the hazards of eating mercury-contaminated fish. EPA conducted community interviews and developed a Community Involvement Plan (CIP). A Community Advisory Group was also formed. Community Advisory Group meetings have been held since 2008. Further community activities will be scheduled as events unfold.

Emergency Response and Removal

Short-term removal work involved site stabilization, which reduced the discharge of acid mine drainage (AMD) and discharge into Las Tablas Creek. In 2000, EPA removed 120,000 cubic yards of contaminated materials from the drainage channel and secured it in an on-site repository to prevent immediate threats to human health and the environment. In 2002, EPA stabilized a sinkhole on site and also stabilized a slope failure on site. In 2006, EPA removed the mercury processing building (retort) and some mercury-laden soils. Contaminated materials stored on site are temporarily capped and will be addressed in the site’s long-term cleanup.